"The Cloud" could mean a lot of things...  I have been using Apple's iCloud for my e-mail and phone for several years, but don't use it on my computer. It works very well with the phone, keeps it backed up whenever you are connected to wifi. Upgrading to a new phone is easy, it will transfer everything so it's just like your old phone. A friend had her phone stolen last year and was really happy when she saw how quickly she was able to restore it to her new phone. Of course, iCloud is a proprietary "Apple Thing" though.
I didn't see much value in online cloud storage for all the years I had slow DSL internet. But now that I'm on very fast FIOS, I have both my primary Mac and my Windows computer on BackBlaze, which constantly backs them up to their cloud. Seems to work very well, you would never even know it's there. I have two other computers that I may eventually add, it costs $50/year per computer. The real test of their service would be actually restoring from their backup, but I don't plan to do that anytime soon. 
 
They caution that it will take a long time to do the first backup, but I set it for maximum speed and then just let it run. It backed up about 300gb on my Mac in less than a day and 700gb on my PC in a little over a day. Even though my FIOS can do 150/150mbs on other sites, the transfer speed was much slower for BackBlaze, something like 30mbs IIRC.
I already had several layers of backup for my important data. But BackBlaze gives me a little more confidence that it can be restored if there's some kind of disaster.